Various types of microscopes are used in the ophthalmic field to observe an enlarged view of the eye. Examples of the ophthalmic microscopes include slit lamp microscopes, surgical microscopes, and the like. Some ophthalmic microscopes include an imaging device to capture images of the eye and a binocular optical system to provide binocular disparity for stereoscopic vision.
The ophthalmic microscope is sometimes used in combination with another ophthalmic device. For example, there are known systems formed of a combination of the ophthalmic microscope and an optical coherence tomography (OCT) device or a laser treatment device (see, for example, U.S. Pat. Nos. 7,599,591 and 8,922,882). The OCT device is used to acquire cross-sectional images and three-dimensional images of the eye, measure the size of a tissue of the eye (retinal thickness, etc.), acquire information on the function of the eye (blood flow information, etc.), and the like. The laser treatment device is used for photocoagulation treatment of the retina or the corner, and the like.
The conventional ophthalmic microscope systems include a Galilean stereomicroscope. The Galilean stereomicroscope is characterized in that the binocular optical system is provided with a common objective lens and that the left and right optical axes of the binocular optical system are parallel to each other. The Galilean stereomicroscope has the benefit of being easily combined with another optical system or an optical element.
Meanwhile, the Galilean stereomicroscope needs an objective lens having a large diameter, and therefore, the degree of freedom in optical design and mechanical design is restricted.
In addition, there is a limit on the distance between the left and right eyes (eye width) of the viewer. Therefore, it is difficult to increase the stereo angle of the binocular optical system, resulting in difficulty of acquiring an observation image having a three-dimensional appearance. In particular, it is extremely difficult to obtain an observation image having a three-dimensional appearance in the observation at a high magnification. On the other hand, it is possible to reduce the stereo angle. However, this requires to place a dedicated optical element (e.g., prism, etc.) in the binocular optical system, which leads to the complication of the structure of the optics. Further, it is also difficult to finely adjust the stereo angle.
A problem exists also in the operability. For example, complicated operation is required for adjusting the focus position according to the observation site. Typically, to shift from the anterior segment observation to the fundus observation, it is necessary to move the microscope in the longitudinal (front-back) direction.
As described above, there are problems in the conventional ophthalmic microscope systems.